The present invention refers to a fixture apparatus that uses a combination of magnetorheological fluids and a special fixture to hold irregular shaped as well as regular shaped work pieces for precision machinery and measurements or other applications that require such apparatus.
It is an applied apparatus making use of a magnetorheological fluid or magneto-viscous fluids. The viscosity of the fluids changes upon application of a magnetic field produced either by a permanent magnet or an electromagnet. A specially designed mechanical fixture is used to hold any regular or irregular shaped work pieces.
In this apparatus, the magnetorheological fluid supplies the average pressure to the work piece that is fastened into it. The special fixture absorbs the extra force, preventing movement or climbing of the work pieces inside the apparatus during machining process.
Previously, a work piece to be machined with an irregular shape was fixed by clamps or some fixtures. Because they solely rely on the force from the clamps or fixtures, the process can cause permanent damage to the work piece. Another way was using a low-melting point metal alloy to hold a work piece by melting the alloy to liquid form, then dipping the work piece into the melted alloy, and then cooling the alloy to hold the work piece. This heating and cooling process will introduce strains in the work piece. Most of the low-melting point alloys have a harmful high vapor pressure, which will damage to the health of the personnel involved and will pollute the environment in the long run.
This invention has solved the long unsolved problem in industry--to firmly hold an irregular shaped work piece in a fixture to perform precision machining and/or measurements without introducing permanent deformation in the work piece or other damages, especially when the work piece is made of heat sensitive or non-magnetic materials. The invented apparatus, naturally, works even better for conventional work pieces with regular shape.
This invention has made magnetorheological fluids enter practical industrial fixture applications. Besides using the applied conventional magnetorheological fluid, a pressure in one or more directions, especially in the magnetic field direction is applied. This will greatly increase the strength of the fluid (i.e., the hold force of the fluid). Most importantly, a special fixture is used to accurately position and hold a work piece inside magnetorheological fluids to prevent the work piece from climbing which is a fatal drawback to the practical applications of magnetorheological fluids. Therefore, this invention overcomes the drawback of conventional fixture apparatus. This makes practical application of magnetorheological fluids in industry or research institutes possible. The obvious advantages of the apparatus compared with other apparatus available are:
i. The phase of a magnetorheological fluid is reversible with the field on or off, which is convenient to use. It can hold any irregular as well as regular shaped work piece firmly for precision machining and/or measurements. PA0 ii. Since no heating or cooling cycle is introduced into the system during the process, the least amount of damage to the work piece is introduced. PA0 iii. The work piece can be any material: metals or non-metals and magnetic materials or non-magnetic materials. PA0 iv. Because magnetorheological fluid is a very good shock absorbing material, the apparatus will reduce the vibration in the work piece due to the processes (i.e., cutting, milling or grinding process). PA0 v. It is environmentally safe.